Contamination of the environment has many potential sources. Environmental clean up is required to contain environmental contamination and thereby prevent further damage to the environment. Contamination of soil occurs when contaminants are spilled or dumped on the ground and percolate into the soil. Materials such as hydrocarbons, degreasers, pesticides, dry cleaning fluids, paint solvents, fertilizers and industrial chemicals frequently percolate into the soil. Clean up of such contaminates is generally difficult. Some materials that percolate into the soil can move downward into ground water and form a plume of contaminated water that eventually reaches wells for drinking water. Clean up of such contaminates is difficult, as mentioned above, because the contaminate will follow a path of least resistance. The location of the path of movement can be difficult to determine. The depth of the contamination may also be difficult to determine. The primary problem will most likely be working in hard compact soil that may not have been disturbed by man.
Chemical, mining and dredging operations create sludge. Sludge produced by these operations and other similar operations has often been placed in settling ponds or lagoons. The solids settle to the bottom in these ponds and the water evaporates over time. The solids as well as some of the liquids in these lagoons are often toxic. Toxic liquids as well as toxic solids are environmental contamination hazards. Toxins may leach into ground water. Heavy rains or fast snow melt may wash toxins into streams or lakes. Wind can blow dry toxins into the air and carry them for miles. Earthquakes can destroy dams made to form sludge ponds and let the sludge run out of a containment.
The toxins in the sludge found in settling ponds and lagoons can be contained to prevent environment contamination by removing the sludge and moving it to a safer containment area. Toxins can also be contained by treatment where they are found. Moving toxins to a new location is generally expensive. There may be millions of tons of material to move. Most people are opposed to having a toxin storage facility in their neighborhood. Finding a suitable storage facility located close to sludge or contaminated soil to be contained is difficult. Contaminated material can be spilled during movement from one site to another.
Treating and containing material contaminated by toxins, where the contaminated material is located, is often the best way to prevent further environmental contamination. The material in a settling pond or lagoon is agitated to turn the sediment into a slurry. After the sediment is turned into a slurry, and additive is mixed with the slurry. The additive can be a liquid or a dry material. The additive generally turns the slurry into a solid. The additive may cause a chemical reaction that reduces the quantity of toxic material or that neutralizes the toxic material.
Converting sediment that is four meters or more under the surface of a lagoon into a slurry can be difficult. It is desirable to treat all material that is contaminated with the additive. All untreated sediment is a potential environmental contaminate. Contaminated sediment that is untreated may over time contaminate an aquifer. Contamination in an aquifer can over time spread and may contaminate water wells.
The grinder mixers employed in the past for sediment agitating have had a drum with teeth mounted on the end of an excavator stick and rotated about a horizontal axis by a hydraulic motor. These rotatable drums are moved vertically and horizontally toward and away from the excavator's vertical pivot axis. Drums with teeth that rotate about a horizontal axis work well for turning sediment into a slurry. However horizontal axis rotating drums with grinder teeth do not work well when mixing in hard compact soil conditions to relatively deep treatment depths. The grinder mixers that have been used to agitate sludge do not work well for reduction or stabilization of soil contaminated by percolation of contaminates.